The present invention relates to a wafer alignment system, and more particularly to a dark field target design system for alignment of semiconductor wafers.
Producing semiconductors requires 10 to 12 layers to be placed on top of each other. The quality of the alignment between each of these layers has a direct effect on circuit yield, the size of the device that can be built and speed of the circuit (performance). Finding an alignment target that is less affected by the semiconductor manufacturing processes, and day to day variations in the process, would directly or indirectly improve all of the above mentioned factors.
The use of dark field alignment systems are the most used automatic field by field alignment systems in the semiconductor industry. These new dark field designs provide the user with more consistent alignment, better alignment than is possible using the current target. Alignment signals will be much less affected by slight process variations while improving overall alignment and productivity.